Current drilling technology, including directional drilling technology, permits the drilling of conventional vertical boreholes which are substantially perpendicular to the ground surface, as well as deviated or non-vertical boreholes. Directional drilling technology also allows for branch, lateral or secondary boreholes to be drilled laterally from a main or primary borehole. Lateral boreholes are often drilled and produced through a gap in the casing of the main borehole. This gap typically comprises a window cut or milled in a section of the existing casing string. The lateral borehole tends to extend laterally from the main borehole to a desired location within the formation. A main borehole including more than one lateral borehole is typically referred to as a multilateral well.
Industry attention has increasingly become more focused upon multilateral wells both with respect to new drilling operations and the reworking of existing boreholes, including remedial and stimulation work (such as Steam Assisted Gravity Drainage applications). As a result, more attention has become focused upon the economics of, and difficulties associated with, the completion and production of multilateral wells. For instance, with respect to the installation of two or more production tubing strings within the multilateral well, particular applications may require the independent production of the main and lateral boreholes to the surface, while other applications may preferably commingle the production to allow the main and lateral boreholes to be produced simultaneously. Further, when installing the tubing strings, the number of necessary trips downhole is preferably minimized in order to increase or maximize the cost effectiveness or profitability of the multilateral well. Finally, the installation of the tubing strings is preferably accomplished in a manner permitting access to the boreholes so that a selected one of the boreholes may be re-entered as desired.
U.S. Pat. No. 5,311,936 issued May 17, 1994 to McNair et. al., U.S. Pat. No. 5,318,121 issued Jun. 7, 1994 to Brockman et. al. and U.S. Pat. No. 5,325,924 issued Jul. 5, 1994 to Bangert et. al. are all directed at various devices and methods for sealing the junction between a lateral and vertical well, for re-entering selected lateral wells to perform completion work, additional work or remedial and stimulation work and for isolating a lateral well from other lateral wells to permit separate production from the lateral well without commingling the production fluids.
More particularly, McNair, Brockman and Bangert all describe the selective re-entry into either the vertical or lateral well by various objects, such as production tubing or tools. Specifically, in each case, the devices and methods described are aimed at selectively permitting the passage of the object through either a main (vertical) borehole or a first branch (lateral) borehole.
For instance, in one embodiment of McNair, Brockman and Bangert, a first coiled tubing conduit is run into the lateral well. The first coiled tubing conduit has a head which is sized and dimensioned such that it will not enter the vertical well but will instead be diverted into the lateral well by a whipstock. Similarly, a second coiled tubing conduit may be separately run into the vertical well. The second coiled tubing conduit has a head which is sized and dimensioned such that it will not enter the lateral well, but may be run into the vertical well through a bore in the whipstock. The first and second coiled tubing conduits are run into their respective wells in two separate steps or two separate trips downhole. There is no further specific discussion regarding the manner in which the first and second coiled tubing conduits are run into the wells.
In a further embodiment of McNair, Brockman and Bangert, a liner may be run into a lateral well using a specialized sidetrack mandrel. The sidetrack mandrel terminates at a housing which may swivel into alignment with the lateral well. Further, the housing includes a laterally extended section which retains a tubing. The tubing is normally stored within the housing for extension into the lateral well. After the sidetrack mandrel is positioned within the vertical well adjacent the lateral well, the tubing is extended through the housing. Upon extension of the tubing, the head of the tubing contacts a whipstock within the vertical well and is thereby diverted into the lateral. There is no specific discussion with respect to the placement or running of tubing within the vertical well when using the sidetrack mandrel.
Alternately, where zone isolation is desired, a modified side pocket mandrel may be used in place of the sidetrack mandrel. The modified side pocket mandrel includes a housing and a dual packer assembly. The housing includes a separate running string which has a pair of shoulders which act as a stop between a sealed position and a non-sealed position. After the modified side pocket mandrel is positioned within the vertical well adjacent the lateral well, the running string is extended through the housing and moved from its non-sealed to its sealed position. Upon extension from the housing, the head of the running string contacts a whipstock and is diverted into the lateral well. Once again, there is no specific discussion with respect to the placement or running of tubing within the vertical well when using the modified side pocket mandrel. However, the dual packer assembly does permit the use of discrete production tubing from the lateral and the vertical wells.
In a still further embodiment of McNair, Brockman and Bangert, a dual completion head is lowered into the vertical well adjacent the lateral well. The dual completion head has an upper deflecting surface and a longitudinal bore. First, a first tubing string may be stung from the surface through the longitudinal bore of the dual completion head. Second, a second tubing string may also be stung from the surface and deflected by the upper deflecting surface of the dual completion head into the lateral well. The first and second tubing strings are run into their respective wells in two separate steps or two separate trips downhole. There is no further specific discussion regarding the manner in which the first and second tubing strings are run into the wells.
U.S. Pat. No. 5,330,007 issued Jul. 19, 1994 to Collins et. al., U.S. Pat. No. 5,458,199 issued Oct. 17, 1995 to Collins et. al., U.S. Pat. No. 5,655,602 issued Aug. 12, 1997 to Collins et. al. and U.S. Pat. No. 5,685,373 issued Nov. 11, 1997 to Collins et. al. are all related to a template, and a process utilizing the template, for drilling and completing multilateral wells.
The template comprises a body having a first end face, a second end face and a plurality of axially extending divergent bores which extend through the body in intersection with the end faces. The template is secured to a first casing, which extends from the surface to a predetermined depth beneath the surface, or is located at or near the ground surface. A first subterranean borehole is drilled through one of the bores in the template and a first length of production casing is secured to the template such that it extends into the first borehole. Similarly, further subterranean boreholes may be drilled through the further bores in the template and further lengths of production casing may be secured to the template such that the casing extends into its respective borehole.
In addition, a generally tubular riser, which is releasably secured to an orienting cam, may be inserted into the plurality of bores in the template. The riser is automatically aligned with one of the bores through the template and is released from the cam. The riser permits the drill string and the casing to pass through a selected bore in the template and into the desired subterranean borehole. Once the boreholes have been drilled and cased, the riser is withdrawn and production casings may be sequentially secured to the casings or bores. As well, conventional production tubing may be inserted into the casings. However, the patents do not include any specific discussion regarding the manner in which the production tubing is run into the boreholes.
As a result, there remains a need in the industry for an improved apparatus and method for the installation of at least two objects, preferably tubing strings, within a borehole. Further, there is a need for an apparatus and a method for concurrently installing a tubing string within each of a primary borehole and at least one secondary borehole. More particularly, there is a need for an apparatus and a method which hold the tubing strings relative to each other and orient the tubing strings relative to the primary and secondary boreholes such that the tubing strings may be directed or installed therein. Preferably, the apparatus and method install the tubing strings in a manner permitting either the production of the primary and secondary boreholes separately or in a commingled production.